Basic facts about colon and rectal cancer staging

Many patients are anxious about the staging of the cancer when they have been diagnosed with colon cancers. This is understandably so as it determines both the overall prognosis of the cancer as well as the treatment necessary to cure it. Below, I will explain some of the basics of colon cancer staging.

A cancer stage is a rating assigned to describe the extent of the cancer. It is used to plan which tests may be needed and which treatments are best for you. The AJCC (American Joint Committee on Cancer) TNM (tumour, node, metastasis) system is used to stage colon cancer.

In the AJCC system, the following key pieces of information about your cancer are used to give it a stage:

 

  • T: How far the cancer has grown through the colon wall
  • N: Whether any lymph nodes have cancer
  • M: Whether the cancer has spread to areas far from the colon (metastasized)

The T, N, and M scores are combined to assign the cancer a stage. There are five stages of colon cancer. They are numbered 0, I, II, III or IV and are explained below.

Stage 0

These cancers are also called carcinoma in situ of the colon. The cancer is non-invasive. This means it has not grown beyond the first layer of the colon wall. You may not need more treatment if a polypectomy has removed all of the cancer.

Stage I

The cancer has grown into either the second or third layer of the colon wall. There is no cancer in nearby lymph nodes or in areas far from the colon.

Stage II

The cancer has grown into, or beyond the fourth layer of the colon wall. There is no cancer in nearby lymph nodes or in areas far from the colon. 

Stage III

The cancer has spread from the colon to nearby lymph nodes or there are tumour deposits. Tumour deposits refer to small tumours found in the fat around the colon.

Stage IV

The cancer has spread to areas far from the colon. Colon cancer often spreads to the liver and the lungs first. 

It is important to note that the final staging is only possible after surgery is done on the cancer and all the above key information is available from the histology and radiology reports. Patient often do not understand that and repeatedly inquire about the final staging even before the operation or soon after the operation.

 Oftentimes an estimation of the staging may be possible based on the pre-operative scans, by studying the extent of tumour growth, the presence of lymph nodes involved as well as metastasis in the liver and/or lung. 

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